1. Field of the Invention
This invention relates broadly to ultrasonic medical imaging systems. More particularly, this invention relates to probes and scanning devices used in combination with needle biopsy assemblies and delivery systems for guided biopsy over askew pathways.
2. State of the Art
Ultrasound scanning is an important diagnostic tool used by medical professionals. Medical devices which employ ultrasound scanning are generally categorized as either cavital imaging devices or body imaging devices. Cavital imaging devices, often referred to as probes, are usually inserted into a cavity of the patient to take and capture images of tissue within and adjacent the cavity. Cavital probes are frequently used to provide transvaginal, transesophagual, and transrectal imaging.
Transrectal probes are important for detecting prostate cancer and rectal cancer, especially for men over the age of fifty. If prostate cancer is suspected after a patient has undergone a physical examination or a Prostate Specific Antigens test, then a biopsy is typically performed to collect tissue samples from the prostate for evaluation by a pathologist. As prostate tumors are small growths which can be scattered about different portions of the prostate, multiple tissue samples (e.g., typically between 9 and 18) are usually taken from the prostate during a biopsy procedure. Performing a biopsy procedure involves inserting a transrectal ultrasonic probe into the rectum of the patient, a procedure known as a Transrectal Ultrasound (TRUS) Guided Prostate Biopsy. The probe, in conjunction with imaging software and associated equipment, generates images of two-dimensional slices of the prostate.
Transrectal ultrasonic probes are also used to provide guidance for transperineal procedures including brachytherapy, cryotherapy or transperineal saturation biopsies. All of these procedures involve inserting needles through a grid through the perineum and utilizing the probe for guidance.
The probe includes one or more ultrasonic transducers which generate a narrow pulse of sound which propagates through surrounding tissue and is reflected back to and captured by the transducer. The density of the tissue and its distance from the transducer effects the properties of the return signal or backscatter received by the transducer. In this manner, the properties of the return signal or backscatter can be used to construct an image of the secondary tissue.
Standard ultrasonic probes contain one or more of such ultrasonic transducers mounted inside a hollow tip. The transducer(s) pivot or quickly rotate within the tip (approximately five to ten times per second) to generate and receive pulses at multiple orientations at a given position of the probe. The probe is used to generate longitudinal images (inline with the axis of the probe) and/or transverse images (perpendicular to the axis of the probe tip). This dual axis image capability is referred to as bi-plane imagining. Solid-state probes utilize a plurality of very small transducers aligned in the probe (e.g. columns wrapped around a small portion of the diameter of the probe and along the length of the probe). Instead of pivoting or rotating a single transducer, the solid state probe sequentially pulses a column of the aligned transducers to create a cross sectional image of the tissue of interest. In this manner, the solid-state probe generates dual axis, bi-plane images.
During an ultrasonically guided prostate biopsy procedure, an ultrasonic probe is inserted into the rectum of the patient adjacent the prostate. Images generated by the probe are used to identify the particular portion(s) of the prostate to biopsy, and to properly position the probe, a guide assembly coupled to the probe, and a needle assembly which is advanced though the guide assembly. The guide assembly guides the distal end of the needle assembly through the rectal wall to a fixed position and orientation adjacent the prostate. Additional images generated by the probe during the procedure help the physician monitor and verify the depth and position of the needle assembly within the prostate.
The needle assembly typically includes a wire shaped biopsy needle and an outer cylindrically shaped cannula which receives and supports the biopsy needle. The needle assembly is often coupled to and operably disposed within a spring loaded instrument, typically referred to as a biopsy gun. The biopsy gun is used to advance the needle of the needle assembly into the prostate. During a first firing of the biopsy gun, the needle rapidly advances relative to the cannula into the prostate over a distance called the stroke length, which is typically between 15 mm to 25 mm. A second firing of the biopsy gun causes the cannula to advance over the exposed notch portion of the needle in the prostate. As the cannula advances over the exposed notch portion of the needle, it cuts and severs tissue surrounding the needle and traps the tissue within the notch portion, thus capturing a tissue sample. The needle and cannula are then withdrawn from the patient with the tissue sample captured within the cannula. This process can be repeated at multiple tissue locations in the prostate.
Controlled movement of a transducer over a range of locations within a probe allows for more accurate and complete imaging, and requires less movement or positioning of the probe. U.S. Pat. No. 5,592,942 to Webler discloses an automated longitudinal position translator for ultrasonic imaging probes, and methods of using such probes within a blood vessel. U.S. Pat. No. 6,004,271 to Moore discloses a combined motor drive and automated longitudinal position translator for an ultrasonic imaging system. U.S. Pat. No. 6,200,269 to Lin, et al discloses a forward scanning ultrasound catheter probe which maintains a transducer on a platform at a distal end of the probe and pivots the platform via a piezoelectric drive to create a scanning plane. Controlled translational and rotational movement of a transducer in a transrectal probe is disclosed in U.S. patent application Ser. No. 11/475,674, and illustrated in FIGS. 15A-15 herein.